I found myself having a hard time answering this as well
Being that Brolly is a movie only characther and Cell is pretty much
a series only characther present's some confusion with the timeline.
And if it matters or not, what movie are we talking about. Brolly was
in three
I myself think that Cell would win. I view Brolly as a USSJ in a
time when Goku, Vegita...etc. could only reach SSJ.
Cell on the other hand when in his perfect form rivals a SSJ2,
especially after coming back after blowing himself up. Cell was able
to wipe the floor with both Vegita and Trunks when they were USSJ's
after leaveing the ROSAT.
So in my opinion cell would win.
Though I'd rather see Brolly win just cause he
relies on his own strengh and doesnt get it from
absorbing others.